The present invention relates to a lockup disconnection period adjustment circuit and, more particularly, to a period adjustment circuit applied to a fan disconnection and restart IC.
Along with progress of science and technology, high power operation of delicate electronic products is increasingly desirable. However, high-power electronic products will easily generate a large mount of heat in use. In addition to cause doubt of safety in use, components of the products will also be easily damaged or even stop functioning. Therefore, most electronic products have cooling fans in design to achieve heat-radiating effect when the products are used.
In the design of a cooling fan, appropriate selection of a motor controller not only can greatly enhance the performance of the fan, but also can ensure heat-radiating effect of the product or equipment. In a conventionally used motor control IC of a DC brushless fan, in order to prevent the rotor of the motor from being locked due to an external factor so as to be unable to operate normally and thus cause the situation of over heat and burnout when the motor operates, a lockup disconnection protection circuit is generally designed in the motor controller to automatically disconnect the electricity and stop the operation of the motor. Therefore, when the rotation of the rotor of the motor is limited, the electricity is automatically disconnected to stop the operation of the motor, hence avoiding continual rise of the temperature of the motor. However, for a disconnection IC used in a conventional disconnection protection type fan, the time and ratio of the lockup disconnection and restart are fixed. Therefore, the present invention adds in a control circuit to adjust the ratio of the periods of the disconnection and restart. Through adjustment of time ratios of the lockup and restart of a fan, the temperature rise of the fan coil can be controlled and adjusted to protect the main structure of the fan motor.
The primary object of the present invention is to provide a period adjustment circuit applied to a fan disconnection and restart IC for adjusting the time and ratio of disconnection and restart, so that the temperature rise of a fan coil can be controlled and adjusted, thereby protecting the fan coil from over heat and burnout.
Another object of the present invention is to let a disconnection and restart IC be capable of flexibly adjusting the period ratio of the disconnection time and restart time thereof so as to apply to all specifications of disconnection ICs.
According to the present invention, a period adjustment circuit of disconnection and restart IC is connected between a disconnection and restart IC and an external first capacitor. The disconnection and restart IC provide a current source to charge the first capacitor. The period adjustment circuit comprises a second capacitor, which is connected to a resistor and a transistor connected in parallel. One end of the resistor is connected between the disconnection and restart IC and the first capacitor. When the disconnection and restart function of the IC is activated, the second capacitor charges the first capacitor via the resistor until the voltage of the first capacitor reaches a disconnection voltage. The IC then enters into the disconnection state, and the voltages of the two capacitors are equal so that the second capacitor no longer charges the first capacitor. Next, the IC current source simultaneously charges the first and second capacitors until the voltage of the first capacitor reaches a system reset voltage. The first capacitor is then discharged to a restart voltage by the IC.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawings, in which: